The invention relates to a method of forming a conductive pattern on a substrate, for example so as to form an electronic circuit.
In one approach to forming very high resolution electrical circuits, for example that used by LPKF Laser and Electronics AG of Germany, a laser is used to cut a narrow line through a layer of a conductive material on an insulating substrate. Complete loops of such cuts are used to isolate areas of conductor which then become the conductive traces of the circuit. This process is useful for forming prototype circuit boards but is slow and the resulting circuit has large areas of unwanted conductor remaining. These are normally left in place since it would take a very long time to use the laser to remove them.
An alternative approach which can be used for low resolution circuits is to define the required circuit as a rasterised image which is then printed, typically using an ink jet printer, over the whole area of the conductive layer using an ink capable of resisting a chemical etch. The required circuit pattern is then produced by etching the conductive layer where it is not covered with the ink, and then removing the ink using another chemical such as a solvent. This process is suitable for producing small volume or prototype products as it is reasonably fast and economical with materials but is not capable of high resolution. This is because of the rasterisation process and the unpredictable behaviour of the printing heads and of the ink on the surface.